GB2317351A

GB2317351A - A tangential flow separator with inner settlement chamber

Info

Publication number: GB2317351A
Application number: GB9619599A
Authority: GB
Inventors: Patrick Todkill; John Todkill
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-09-19
Filing date: 1996-09-19
Publication date: 1998-03-25
Also published as: AU4215897A; GB9619599D0; WO1998011976A1

Abstract

A tangential flow separator comprises a substantially cylindrical outer separation chamber, an inlet 25 tangential to the wall of the separation chamber causing heavier and lighter entrained particles to separate out from the fluid under a centrifugal force, arrows A, C, a concentric inner settlement chamber and a central clean fluid outlet conduit from the inner settlement chamber passing through both chambers along their common axis. Particles still entrained in the fluid entering the inner settlement chamber can settle out under the now predominant force of gravity due to the decreased angular velocity. Placing the central outlet conduit orifices away from the central axis ensures particles are not extracted by virtue of being purely in a low angular velocity under no centrifugal forces. A baffle (47, fig 1b) may be provided to break up any cyclonic flow entering the settlement chamber 42. The apparatus may be only single ended (fig 1) or for gaseous carrier flow.

Description

IMPROVEMENTS IN AND RELATING TO FLUID SEPARATION DEVICES The present invention relates to separation devices for separating particulate matter and contaminants from carrier fluids and in particular to those deploying tangential flow separation techniques.

In tangential flow separators known in the art, a base fluid which is contaminated with particulates is fed tangentially into a pre-charged elongate tube of circular cross-section at an inlet which is situated in the circular wall of the tube. The tangential ingress of the contaminated fluid generates a laminar vortex flow of the fluid within the tube. The laminar vortex flow causes heavy contaminates within the fluid to remain close to the tube wall, with decontaminated fluid found on and near the central axis of the tube.

Typically, the decontaminated fluid is then drawn off from the central axis of the tube in an upward axial direction by an outlet pipe extending down into the tube on its axis and having an outlet orifice which is orthogonal to the tube. Particulates which have been propelled toward the outer circular wall of the tube may then be extracted by routine removal from the sides of the tube, or by a draw off point at the base of the tube to which heavy particulates will gradually migrate under the influence of gravity.

A particular problem with such tangential flow separators is that particle contaminates which are at or close to the central axis of the tube will simply be drawn off into the outlet pipe because the particle energy near the axis is very low. The radially outward (centrifugal) force is therefore correspondingly low and insufficient to convey the particles in a radially outward direction.

A further problem with prior art separators is that where fluid flows through the separator are sufficiently high, the flows through the outlet pipe are sufficient to cause a general flow toward the outlet pipe which will carry unwanted particulates toward the outlet, ie., counteracting any centrifugal force separating the particulates.

Thus, in both cases, there is a tendency for the outlet pipe to draw out particulates which have not been properly separated by the tangential flow.

It is an object of the present invention to provide a tangential flow separator which overcomes these particular problems.

The present invention improves upon the separation of contaminants from the base fluid by providing a tangential flow separator with a generally extended fluid path length between an inlet and an outlet without extending the distance between the inlet and a particulate collecting zone.

The present invention provides a settlement zone in the extended path, between the inlet and the outlet, which settlement zone lies beyond a separation zone lying between the inlet and the particle collection zone.

According to another aspect, the present invention provides an outlet aperture which draws off decontaminated fluid in a radially inward direction through apertures displaced from the axis of the separator thereby ensuring that outflow of decontaminated fluid is taken only from a zone of the separator in which the fluid has a predetermined minimum angular velocity.

According to another aspect, the present invention provides a tangential flow separator comprising: a separation chamber defined by a substantially circular outer wall extending along an axis of the chamber between a first end and a second end of the chamber; an inlet adapted to direct fluid into the chamber in a substantially tangential direction; an outlet located at or close to the chamber axis; a settlement chamber surrounding the outlet, having a substantially circular outer wall concentric with the separation chamber outer wall and extending along the axis part way between the first and second ends of the separation chamber.

According to another aspect, the present invention provides a tangential flow separator comprising: a separation chamber defined by a substantially circular outer wall extending along an axis of the chamber between a first end and a second end of the chamber; an inlet adapted to direct fluid into the chamber in a substantially tangential direction; an outlet comprising a pipe extending into the separation chamber and including at least one orifice which is radially displaced from the central axis of the chamber.

According to another aspect, the present invention provides a tangential flow separator having an inlet adapted to direct fluid into a separation chamber in a substantially tangential direction, a particulate collection zone in a radially outward portion of the separation chamber, an outlet for drawing off decontaminated fluid from the separator, and a settlement zone lying between the separation zone and the outlet and at least partly separated from the separation zone by an inner wall.

Embodiments of the present invention will now be described by way of example and with reference to the accompanying drawings in which: Figure 1 shows a schematic diagram of a single ended tangential flow separator including: in figure l(a), a bottom plan view of a half section of the separator; in figure l(b), a side cross-sectional view of the separator; and in figure l(c), a top plan view of the half section of the separator; Figure 2 shows a schematic diagram of a double ended tangential flow separator including: in figure 2(a), a side cross-sectional view of the separator; and in figure 2(b), a top or bottom plan view of the separator; Figure 3 shows a schematic diagram of a single ended tangential flow separator according to an alternative embodiment.

With reference to figure 1 there is shown a tangential flow separator 10 according to one embodiment of the present invention. The separator 10 comprises a separation chamber 15 which is defined by a circular cylindrical outer wall 20 about the chamber axis 12, the outer wall 20 extending down to conical tapered portion 22 at a first (lower) end of the separation chamber 15, and being open at a second (upper) end of the separation chamber 15. An inlet pipe 25 is connected to an opening in the outer wall 20 towards the upper end of the separation chamber and extends tangentially away from the outer wall.

Also centred on the separator axis 12 is an outlet pipe 30 which extends along the axis 12, through the separation chamber 15. The outlet pipe includes one or more outlet orifices 32,33 in the wall of the pipe allowing fluid to pass from the chamber into the outlet pipe 30.

Also centred on the separator axis 12 is a settlement chamber 40 defined by a circular cylindrical inner wall 42, ie. which is concentric with the circular outer wall 20. The inner wall extends down to a tapered portion 44 at a first (lower) end of the settlement chamber 40 and is open at the second (upper) end of the settlement chamber 40. Fluid is able to pass between the separation chamber 15 and the settlement chamber 40 by way of an aperture 46 in between the lower end of the settlement chamber wall 42 and the outlet pipe 30. Preferably the aperture 46 has a crosssectional area which is greater than the cross-sectional area of the outlet orifices 32,33. Preferably the aperture 46 incorporates a flow modifier device 47 which acts as a baffle to fluid passing between the separation chamber 15 and the settlement chamber 40 and generates non-laminar (turbulent) flow into the settlement chamber. Such flow modifiers enhance the performance of the separator, particularly when handling contaminated fluids in which the contaminant has a density similar to that of the carrier medium.

The outer wall 20 of the separator 10 also includes a plurality of apertures 26 used to draw off contaminant particulates from the separation chamber 15. These may be coupled to suitable pipes or to a collection vessel in which the entire separator or lower part thereof is incorporated, not shown.

In use, contaminated fluid is admitted under pressure to the separator 10 by way of the inlet pipe 25 which causes the fluid to move through the separation chamber 15 in a vortex flow, substantially filling the separator. As the fluid level rises, the settlement chamber 40 also fills with fluid at least up to the level of the outlet pipe orifices 32,33.

Normally, this constitutes a pre-charging operation, after which the separator will operate in steady-state condition, ie. full or stable fluid level.

The vortex flow of contaminated fluid forces the separation of particulates and other contaminants from the base fluid, the particulates being forced to the outer wall 20 by centrifugal force. Gravitational forces cause the gradual migration of the particulates to the bottom of the separation chamber 15, ie. into the conical end portion 22, where they are continuously extracted via the contaminant outlet apertures 26, as indicated by arrow A on figure l(b). Contaminants or particulates which are lighter than the fluid medium will tend to collect against the inner wall 42 from where they will gradually rise to the top of the separation chamber 15, as indicated by arrow C. From there, they may be removed by a weir or similar suitable unrestricted outlet.

Decontaminated fluid tends to collect at a radially central part of the separation chamber 15 at the input level, and alsoat a radially inward part of the separation chamber lower down ie. where the lighter particulates have floated out, ie. following the first part of arrow B. As decontaminated fluid enters the settlement chamber 40 through aperture 46, a flow of decontaminated fluid is set up as indicated by arrow B in figure l(b). As the decontaminated fluid enters the settlement chamber 40, the flow velocity falls owing to the geometry of the lower portion of the settlement chamber and any flow modifier present in the aperture 46.

Any contaminant which has failed to be removed from the generally decontaminated fluid will tend to be obstructed from entry into the settlement chamber by the action of the flow modifier at aperture 46, or will tend to settle out in the reduced energy zone of the settlement chamber 40.

The occluding of the radially inward portions of the separation chamber 15 by the inner wall 42 is advantageous in minimizing or eliminating any slowly moving fluid from the separation chamber, thereby ensuring that particles within the fluid are effectively moved to the outer wall 20.

The geometry of the settlement chamber and the aperture between the separation chamber 15 and the settlement chamber 40 are determined according to the required application of the tangential flow separator.

Factors such as the relative density of the carrier fluid to contaminants and flow rates must be taken into account when optimising the design.

Turning now to figure 2, there is shown a further embodiment of the invention which is advantageous for separating out contaminants which have both higher relative density with respect to the carrier fluid medium and contaminants which have a lower relative density to the carrier fluid medium, such as flock. In this embodiment, a separator 100 is similar to that described in connection with figure 1, but includes an upper end portion 52 of the separation chamber 15 which is preferably a mirror image of the lower end portion 22, and an upper end portion 54 of the settlement chamber 40 which is preferably a mirror image of the lower end portion 44. Energized lighter particles or flocks will similarly be accumulated near to the inner wall 42 of the separation chamber 15 where they will rise to the upper end portion 52 to be extracted from the separation chamber via contaminant outlets 56, as indicated by arrows C.

Decontaminated fluid will be drawn into the settlement chamber 40 either from below (arrow B1) or from above (arrow B. In similar manner to that described above in relation to the apertures 46 connecting separation chamber 15 from settlement chamber 40, floating particulates carried into the settlement chamber 40 will tend to rise out of the chamber through apertures 58. The apex of the upper end portion 52 may be provided with air vents for egress of gaseous material which could otherwise collect there.

It will be understood, therefore, that the settlement chamber forms a quiet zone in which particles will have a low energy. Gravitational forces are therefore able to dominate over those provided by the fluid motion, causing the particulates to either sink out of the settlement chamber or float out of the settlement chamber dependent upon their specific gravity. The embodiment of figure 2 thus has the advantages of enabling efficient removal of both heavy and light contaminants from a carrier fluid within a single piece of apparatus.

The dual ended configuration of separator of figure 2 also confers significant advantages with respect to temperature immunity of the system.

Because the relative density of the contaminants to the carrier fluid is a function of temperature, a separator design adapted to remove particulates from a lower end of the separation chamber may fail to function correctly as temperatures fall because the density of the carrier fluid increases faster than that of the contaminants. Similar problems may occur in reverse.

The dual ended system operates independently of temperature.

The separators of figures 1 and 2 may be varied in a number of ways. For example, it is not essential that the outlet pipe extends through the entire length of the settlement chamber 15 or separation chamber 40.

The pipe may extend in from one end and terminate at a convenient location within the settlement chamber 40. The orifices 32,33 may be of any suitable number, located around the circumference of the outlet pipe 30, or may be a simple single orifice defined by the end of the pipe, ie.

facing upward or downward in the plane perpendicular to the axis 12.

The orifices may include a mesh filter or the like.

Although shown as circular cylindrical chambers with conical tapers at the ends thereof, the separation and settlement chambers may be differently shaped provided that the appropriate vortex flow around the separation chamber can be achieved.

With reference now to figure 3, there is shown a further separator according to the present invention. The separator 200 includes a separation chamber 215 and inlet pipe 225 similar to that described in connection with figures 1 and 2. The outlet pipe extends at least part way through the separation chamber along the axis thereof, preferably the full extent of the length of the chamber, as shown in dotted outline. Outlet pipe orifices 232,233 are provided in the circumferential wall of the outlet pipe such that they act to extract fluid from the chamber in a radially inward direction, rather than extracting fluid in an axial direction from a stagnant zone on the axis.

The distance of the outlet pipe orifices 232,233 from the axis (ie.

the gauge of the pipe 230) determines the angular velocity of the fluid at the point of extraction. An important aspect here is that the outlet orifice is provided off the central axis of the separation chamber and thus fluid is not drawn off from a zone in which particles may reside by virtue of the fact that the fluid in that zone has zero or low angular velocity. It will be understood that this could be achieved by an off-axis pipe extending into the separation chamber.

It will be understood that, in any of the preceding embodiments, removal of the sludge or scum from the bottom or top of the separation chamber through apertures 26, 56 may be effected intermittently or in a continuous mode, dependent upon the application, eg. taking into account the ratio of contaminant to carrier fluid. In the latter case, a continuous negative pressure may be applied to the restricted apertures 26,56 to maintain a minimum velocity of fluid and contaminants out of the apertures 26,56 in order to counteract tendency of particulates to enter the settlement chamber 40. Apertures 26,56 may lead to a further chamber for collection of the contaminants.

Although the present invention has so far been described with reference to a single separation chamber 15 and a single settlement chamber 40, it will be understood that a multi-stage separator could be deployed, for example using several successive settlement tanks within the separator, each successive chamber being filled with fluid having lower energy than the previous chamber.

The separators herein described may also operate in a recirculation mode, in which the chambers are always pre-charged with fluid. This is achieved by use of an appropriate feedback loop by which a proportion of decontaminated fluid is recirculated to the input. This ensures that minimum flow velocities are maintained in the separation chamber for all input flows, ensuring correct operation of the settlement zone within the settlement chamber.

Claims

1. A tangential flow separator comprising: a separation chamber defined by a substantially circular outer wall extending along an axis of the chamber between a first end and a second end of the chamber; an inlet adapted to direct fluid into the chamber in a substantially tangential direction to said outer wall; an outlet located at or close to the chamber axis; a settlement chamber surrounding the outlet, having a substantially circular outer wall concentric with the separation chamber outer wall and extending along the axis part way between the first and second ends of the separation chamber.

2. A tangential flow separator according to claim 1 further including a settlement tank inlet located at at least one end of the settlement tank between the settlement chamber outer wall and the axis.

3. A tangential flow separator according to claim 2 in which the settlement chamber outer wall includes a conical portion at one end thereof, tapering toward the axis, the settlement chamber inlet located between one end of the conical portion and the axis.

4. A tangential flow separator according to claim 3 in which the settlement chamber outer wall includes a conical portion at both ends thereof, tapering toward the axis.

5. A tangential flow separator according to claim 2, claim 3 or claim 4 further including a flow modifier situated in the settlement chamber inlet.

6. A tangential flow separator according to any preceding claim in which the outlet includes a pipe extending into the separation chamber and into the settlement chamber along the axis.

7. A tangential flow separator according to claim 6 in which the outlet pipe includes at least one orifice on an outer wall thereof adapted to draw off fluid from the settlement chamber in a radially inward direction.

8. A tangential flow separator according to any preceding claim in which the separation chamber includes at least one contaminate draw off aperture at one of the first or second ends thereof.

9. A tangential flow separator according to claim 8 dependent from claim 3 in which the at least one draw off point is situated on the tapered conical portion away from the chamber axis.

10. A tangential flow separator according to claim 9 further including a second contaminate draw off point at the opposite end of the separation chamber to the first contaminate draw off point.

11. A tangential flow separator according to claim I in which the first end of the separation chamber is an open end and the second end of the separation chamber includes restricted outlets.

12. A tangential flow separator according to claim 1 in which the first and second ends of the separation chamber include restricted outlets.

13. A tangential flow separator comprising a separation chamber defined by a substantially circular outer wall extending along an axis of the chamber between a first end and a second end of the chamber; an inlet adapted to direct fluid into the chamber in a substantially tangential direction; an outlet comprising a pipe extending into the separation chamber and including at least one orifice which is radially displaced from the central axis of the chamber.

14. A tangential flow separator according to claim 13 in which the outlet pipe extends into the separation chamber along the axis thereof and in which said at least one orifice is provided in an outer wall of the pipe thereby being adapted to draw off fluid from the separation chamber in a radially inward direction.

15. A tangential flow separator having an inlet adapted to direct fluid into a separation chamber in a substantially tangential direction, a particulate collection zone in a radially outward portion of the separation chamber, an outlet for drawing off decontaminated fluid from the separator, and a settlement zone lying between the separation zone and the outlet and at least partly separated from the separation zone by an inner wall.